The second and latest Two-Micron All Sky Survey 2MASS for short data release makes available images covering a staggering 48 percent of the sky. Among the images is everything from the center of the Milky Way to fields thick with stars to breathtaking views of swirling galaxies.

The $30 million NASA- and National Science Foundation- funded project uses two 51-inch (1.3-meter) automated telescopes at Mt. Hopkins, Arizona and Cerro Tololo, Chile to scan the sky. The survey work, begun in 1997, has covered 95 percent of the sky. Observational work winds up next year, with the last of the data slated to be released by 2003.

The current release of data, freely available on the web, can make literal armchair astronomers out of even the most dedicated professional scientists. Any computer with a web browser can be turned into an observatory that can function day or night, rain or shine, anywhere in the world.

"In some sense, its like a virtual observatory," said Roc Cutri, the 2MASS project scientist. "If you want to view a particular piece of sky, you put in a query and the database goes and fetches that."

The census of stars detects infrared wavelengths beyond the red light in the spectrum of visible colors. That allows the project to peer through the dust and gas that fills our galaxy and bring to view the heat of extremely cool objects otherwise invisible to optical telescopes.

In fact, that capability has prompted a shakeup of the classification system for known types of stars with the discovery of L-dwarfs, the coolest brown dwarfs or failed stars ever uncovered.

"These stars will probably turn out to be most numerous stars in the galaxy, and we didnt know about them five years ago," Cutri said.

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